For purposes of exemplary showings, the teachings of the present invention will be described in their application to cutter bit carrying lugs and base members mounted on the driven element of a mining machine. It will be immediately apparent, however, to one skilled in the art that the teachings of the present invention may be readily applied to work tool carrying lugs and base members mounted on the driven elements of other types of earthworking and digging machines. Such applications of the teachings of the present invention to earthworking and digging machines can readily be accomplished by one skilled in the art without the exercise of invention. Therefore, such terms as "cutter bit", "mining machine", and "cutting direction" are intended to be broadly interpreted to include digger teeth and the like, earthworking and digging machines and digging direction, respectively.
There are many types of well known mining machines. They all have one thing in common in that they are provided with some form of driven element adapted to support one or more, and usually a plurality of, cutter bit-lug assemblies and to drive such assemblies in a cutting direction against the material being mined. As indicated above, the driven elements of mining machines may take many forms. A non-limiting list of such driven elements includes cutter chains, cutter bars, cutter arms, cutter wheels, cutter drums, oscillating rippers, longwall cutters and the like.
In normal mining operations, cutter bits require frequent replacement due to wear or breakage. It is not unusual for cutter bits to be replaced on a daily basis. The cutter bits are mounted in lugs and the prior art has done much work on the provision of cutter bits which are readily replaceable with respect to their mounting lugs, having developed, among other things, a variety of cutter bits having a "knock-in, pry-out" mounting relationship with respect to their lugs and bits having readily removably retaining means maintaining them in their respective lugs.
The lug means in which the cutter bits are held, on the other hand, are characterized by a longer service life. As a result, the most common practice heretofore has been to permanently affix the lugs to the driven elements of the mining machines as by welding or the like. Nevertheless, the lugs themselves are subject to wear and breakage. Under extremely severe conditions, lugs may require replacement on a weekly basis.
Since the lugs have usually been welded or otherwise permanently affixed to the driven element of the mining machine, their replacement has been difficult. Where possible, their replacement has been attempted in the field. Frequently, however, it has been necessary to remove the driven element from the mining machine and to take it to a place where repairs can be made. In either event, lug replacement has been a difficult and time consuming procedure resulting in considerable down time for the mining machine.
As a consequence, it is not unusual that replacement of one or more broken lugs was postponed until the operator of the mining machine simply had no other alternative. However, when broken or worn lugs are not replaced, the efficiency of the mining machine is diminished and an undue strain is placed upon adjacent bits and lugs. One or more broken lugs can also result in the production of float dust which not only renders the mining operation more difficult, but also constitutes a hazard to the health.
Only recently have prior art workers expended effort in overcoming the problem of providing a readily replaceable cutter bit lug. Exemplary recent prior art approaches are set forth in United States Letters Pat. No. Re. 28,310 and United States Letters Pat. No. 4,057,294. The first of the above mentioned U.S. Patents is directed primarily to a lug and base member assembly wherein the lug is affixed to the base member by a removable pin which passes transversely through portions of the base member and the lug. The base member and lug are so configured as to reduce the resultant cutting forces sustained by the pin.
The last mentioned United States Patent teaches a different approach wherein the cutter bit lug and the base member have a wedging relationship and the retaining means for the lug takes the form of a wedging device adapted to implement the wedging relationship between the lug and base member so as to prevent undesired disengagement of the lug from the base member. Again, all of the retaining means taught in this reference are subject to the resultant cutting forces during the mining operation.
The present invention is directed to a base member which may be permanently affixed to the driven element of a mining machine and to a cutter bit carrying lug which is removably mounted on the base member. A retaining means is also provided to assure against undesired disengagement of the lug from the base member. The lug and base member have a wedging interengagement. In all of the embodiments, the retaining means does not constitute an integral part of the lug and can be installed after the lug is mounted on the base member. In all but two of the embodiments of the present invention the retainer is free of resultant cutting forces. In all but three of the embodiments, the retaining means is located exteriorally of the lug. Finally, in only one of the embodiments of the present invention does the retaining means extend transversely through portions of both the base member and the lug.